<p>The PseI protein catalyses the final step of pseudaminic acid biosynthesis, the condensation of PEP with 6-deoxy-beta-L-AltNAc4NAc to generate pseudaminic acid [<cite idref="PUB00045365"/>]. PseI is part of a broader family of synthases that includes the NeuB protein involved in the PEP-dependent biosynthesis of neuraminic acid.</p>